There are recently increasing demands for high-powered and small-sized drive motors to be mounted in hybrid electric vehicles and others. For this purpose, a method of forming a coil by edgewise bending a flat rectangular conductor having a rectangular cross section (a “flat rectangular conductor”) has been studied.
The use of the flat rectangular conductor makes it possible to increase the cross sectional area of the conductor and improve the space factor. As the conductor has a wider cross sectional area, the resistance decreases, thus suppressing heat generation in a motor. However, a demerit of this configuration is difficulty in winding.
Further, a coil formed of the flat rectangular conductor or a coil formed of a conductor wire having a circular cross section needs to be connected with a bus bar in a coil end. For this purpose, various methods of connecting a conductor and a bus bar in a coil end have also been studied.
Patent Document 1 discloses a welding structure of a bus bar and a welding method thereof.
An end of a wire having a circular cross section exposed on a coil end is provided as an end portion of a coil wound in a core assembly. A bus bar engaged with this wire end is formed with a slit at its distal end. When the slit and the wire end are engaged, the coil forms an electric circuit of a rotary electric machine. The wire end is inserted in the slit of the bus bar and then welded to engage with the bus bar.
Patent Document 2 discloses a technique related to a connecting method with respect to a terminal.
A plurality of U-shaped coils are inserted in a stator core and bus bar plates each formed with cutouts are joined to cylindrical terminal portions formed in a coil end of each U-shaped coil, thereby forming an electric circuit of the coils. The joining is performed by TIG welding or other techniques.